the voltage gradient. The water velocity with- 

 in the electrical field should be 3 feet per second 

 or greater if fish mortality is to be eliminated. 

 To provide a positive barrier the minimum bar- 

 rier voltage should be 0.5 volts per inch with a 

 field length of 10 feet in which the voltage grad- 

 ient may vary from 0.3 to 0.7 volts per inch. 



Adult salmon may be conditioned to an 

 electrical field and the field may then be used 

 to lead and collect the fish for diversion into 

 holding ponds . 



Comparisons of survival rates between 

 years of both the diverted adult salmon and 

 their resulting progeny indicate that no measur- 

 able difference in survival exists between fish 

 diverted by the electrical field and by a picket 

 weir. 



The electrical field offers no barrier or 

 source of mortality to downstream migrant 

 salmon fingerlings. Such fish, 4 to 5 inches in 

 length, move through the field with impunity . 



The Entiat type of electrical weir is par- 

 ticularly applicable to salmon -cultural operations 

 where it is desirable to divert the adult fish into 

 holding areas. In comparison with conventional 

 mechanical barriers it is more adaptable to a 

 variety of stream conditions, more economical 

 to install and maintain, and a mpre positive 

 barrier at all water stages. Tests of this weir 

 have been limited to stream widths of not more 

 than 200 feet and depths less than 8 feet. Its 

 application in larger streams remains to be 

 evaluated. 



LITERATURE CITED 



Applegate, Vernon, C, Bernard R. Smith, and 

 Willis L. Nielsen 



1952 . Use of electricity in the control of 

 sea lampreys: electromechanical 

 weirs and traps and electrical bar* 

 riers. U.S. Fish and Wildlife 

 Service, Spec. Sci. Rept.--Fish. 

 No . 92, 52 pp . 



Andrew, F. J., P.C. Johnson, andL. R. Kersey 

 1956. Electric screens for adult salmon. 



International Pacific Salmon Fisheries 

 Comm., Progress Rept., 43 pp. 



Holmes, Harlan B. 



1948. History, development, and problems 

 of electric fish screens. U.S. 

 Fish and Wildlife Service, Spec. 

 Sci. Rept. No. 53, 62 pp. 



McLain, Alberton L., and Willis L. Nielsen 



1953. Directing the movement of fish with 

 electricity. U.S. Fish and Wildlife 

 Service, Spec. Sci. Rept. --Fish. 

 No. 93, 24 pp. 



McMillan, F. O. 



1928. Electric fish screen. Bull. U.S. 

 Bur. of Fish., Vol. 44, pp. 97-128. 



11 



INT.-DUP. SEC. WASH., O.C. 



